A solution contains `Fe^(2+), Fe^(3+)` and `T^(-)` ions. This solution was treated with iodine at `35^(@)C. E^(@)` for `Fe^(3+), Fe^(2+)` is `0.77 V` and `E^(@)` for `I_(2)//2I^(-)` = 0.536 V. The favourable redox reaction is:

Options

A. `I^(-)` will be oxidised to `I_(2)`
B. `Fe^(2+)` will be oxidised to `Fe^(3+)`
C. `I_(2)` will be reduced to `I^(-)`
D. There will be no redox reaction

Answer

To solve the problem, we need to determine the favorable redox reaction involving the ions present in the solution: \( \text{Fe}^{2+} \), \( \text{Fe}^{3+} \), and \( \text{I}^- \). We are given the standard reduction potentials for the relevant half-reactions.

### Step 1: Identify the half-reactions and their standard reduction potentials
The relevant half-reactions and their standard reduction potentials (\( E^\circ \)) are:
1. \( \text{Fe}^{3+} + 3e^- \rightarrow \text{Fe}^{2+} \) with \( E^\circ = 0.77 \, \text{V} \)
2. \( \text{I}_2 + 2e^- \rightarrow 2\text{I}^- \) with \( E^\circ = 0.536 \, \text{V} \)

### Step 2: Determine which species will be reduced and which will be oxidized
To determine which species will undergo reduction and which will undergo oxidation, we compare the standard reduction potentials:
- Since \( E^\circ \) for \( \text{Fe}^{3+}/\text{Fe}^{2+} \) (0.77 V) is greater than \( E^\circ \) for \( \text{I}_2/\text{I}^- \) (0.536 V), \( \text{Fe}^{3+} \) will be reduced to \( \text{Fe}^{2+} \), and \( \text{I}^- \) will be oxidized to \( \text{I}_2 \).

### Step 3: Write the balanced redox reaction
The balanced redox reaction can be written as follows:
- Reduction: \( \text{Fe}^{3+} + 3e^- \rightarrow \text{Fe}^{2+} \)
- Oxidation: \( 2\text{I}^- \rightarrow \text{I}_2 + 2e^- \)

To balance the electrons, we multiply the oxidation half-reaction by 3:
- \( 6\text{I}^- \rightarrow 3\text{I}_2 + 6e^- \)

Combining both half-reactions gives:
\[ 2\text{Fe}^{3+} + 6\text{I}^- \rightarrow 2\text{Fe}^{2+} + 3\text{I}_2 \]

### Step 4: Conclusion
The favorable redox reaction is:
\[ 2\text{Fe}^{3+} + 6\text{I}^- \rightarrow 2\text{Fe}^{2+} + 3\text{I}_2 \]